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187 lines
5.9 KiB
187 lines
5.9 KiB
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
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<html>
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<head>
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<title>Lua/C API Extensions</title>
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<meta name="Author" content="Mike Pall">
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<meta name="Copyright" content="Copyright (C) 2005-2013, Mike Pall">
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<meta name="Language" content="en">
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<link rel="stylesheet" type="text/css" href="bluequad.css" media="screen">
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<link rel="stylesheet" type="text/css" href="bluequad-print.css" media="print">
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</head>
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<body>
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<div id="site">
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<a href="http://luajit.org"><span>Lua<span id="logo">JIT</span></span></a>
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</div>
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<div id="head">
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<h1>Lua/C API Extensions</h1>
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</div>
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<div id="nav">
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<ul><li>
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<a href="luajit.html">LuaJIT</a>
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<ul><li>
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<a href="http://luajit.org/download.html">Download <span class="ext">»</span></a>
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</li><li>
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<a href="install.html">Installation</a>
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</li><li>
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<a href="running.html">Running</a>
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</li></ul>
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</li><li>
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<a href="extensions.html">Extensions</a>
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<ul><li>
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<a href="ext_ffi.html">FFI Library</a>
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<ul><li>
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<a href="ext_ffi_tutorial.html">FFI Tutorial</a>
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</li><li>
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<a href="ext_ffi_api.html">ffi.* API</a>
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</li><li>
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<a href="ext_ffi_semantics.html">FFI Semantics</a>
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</li></ul>
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</li><li>
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<a href="ext_jit.html">jit.* Library</a>
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</li><li>
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<a class="current" href="ext_c_api.html">Lua/C API</a>
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</li></ul>
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</li><li>
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<a href="status.html">Status</a>
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<ul><li>
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<a href="changes.html">Changes</a>
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</li></ul>
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</li><li>
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<a href="faq.html">FAQ</a>
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</li><li>
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<a href="http://luajit.org/performance.html">Performance <span class="ext">»</span></a>
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</li><li>
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<a href="http://wiki.luajit.org/">Wiki <span class="ext">»</span></a>
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</li><li>
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<a href="http://luajit.org/list.html">Mailing List <span class="ext">»</span></a>
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</li></ul>
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</div>
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<div id="main">
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<p>
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LuaJIT adds some extensions to the standard Lua/C API. The LuaJIT include
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directory must be in the compiler search path (<tt>-I<i>path</i></tt>)
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to be able to include the required header for C code:
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</p>
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<pre class="code">
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#include "luajit.h"
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</pre>
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<p>
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Or for C++ code:
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</p>
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<pre class="code">
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#include "lua.hpp"
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</pre>
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<h2 id="luaJIT_setmode"><tt>luaJIT_setmode(L, idx, mode)</tt>
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— Control VM</h2>
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<p>
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This is a C API extension to allow control of the VM from C code. The
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full prototype of <tt>LuaJIT_setmode</tt> is:
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</p>
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<pre class="code">
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LUA_API int luaJIT_setmode(lua_State *L, int idx, int mode);
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</pre>
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<p>
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The returned status is either success (<tt>1</tt>) or failure (<tt>0</tt>).
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The second argument is either <tt>0</tt> or a stack index (similar to the
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other Lua/C API functions).
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</p>
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<p>
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The third argument specifies the mode, which is 'or'ed with a flag.
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The flag can be <tt>LUAJIT_MODE_OFF</tt> to turn a feature on,
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<tt>LUAJIT_MODE_ON</tt> to turn a feature off, or
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<tt>LUAJIT_MODE_FLUSH</tt> to flush cached code.
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</p>
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<p>
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The following modes are defined:
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</p>
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<h3 id="mode_engine"><tt>luaJIT_setmode(L, 0, LUAJIT_MODE_ENGINE|flag)</tt></h3>
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<p>
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Turn the whole JIT compiler on or off or flush the whole cache of compiled code.
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</p>
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<h3 id="mode_func"><tt>luaJIT_setmode(L, idx, LUAJIT_MODE_FUNC|flag)</tt><br>
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<tt>luaJIT_setmode(L, idx, LUAJIT_MODE_ALLFUNC|flag)</tt><br>
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<tt>luaJIT_setmode(L, idx, LUAJIT_MODE_ALLSUBFUNC|flag)</tt></h3>
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<p>
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This sets the mode for the function at the stack index <tt>idx</tt> or
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the parent of the calling function (<tt>idx = 0</tt>). It either
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enables JIT compilation for a function, disables it and flushes any
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already compiled code or only flushes already compiled code. This
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applies recursively to all sub-functions of the function with
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<tt>LUAJIT_MODE_ALLFUNC</tt> or only to the sub-functions with
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<tt>LUAJIT_MODE_ALLSUBFUNC</tt>.
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</p>
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<h3 id="mode_trace"><tt>luaJIT_setmode(L, trace,<br>
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LUAJIT_MODE_TRACE|LUAJIT_MODE_FLUSH)</tt></h3>
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<p>
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Flushes the specified root trace and all of its side traces from the cache.
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The code for the trace will be retained as long as there are any other
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traces which link to it.
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</p>
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<h3 id="mode_wrapcfunc"><tt>luaJIT_setmode(L, idx, LUAJIT_MODE_WRAPCFUNC|flag)</tt></h3>
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<p>
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This mode defines a wrapper function for calls to C functions. If
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called with <tt>LUAJIT_MODE_ON</tt>, the stack index at <tt>idx</tt>
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must be a <tt>lightuserdata</tt> object holding a pointer to the wrapper
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function. From now on all C functions are called through the wrapper
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function. If called with <tt>LUAJIT_MODE_OFF</tt> this mode is turned
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off and all C functions are directly called.
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</p>
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<p>
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The wrapper function can be used for debugging purposes or to catch
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and convert foreign exceptions. But please read the section on
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<a href="extensions.html#exceptions">C++ exception interoperability</a>
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first. Recommended usage can be seen in this C++ code excerpt:
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</p>
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<pre class="code">
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#include <exception>
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#include "lua.hpp"
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// Catch C++ exceptions and convert them to Lua error messages.
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// Customize as needed for your own exception classes.
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static int wrap_exceptions(lua_State *L, lua_CFunction f)
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{
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try {
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return f(L); // Call wrapped function and return result.
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} catch (const char *s) { // Catch and convert exceptions.
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lua_pushstring(L, s);
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} catch (std::exception& e) {
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lua_pushstring(L, e.what());
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} catch (...) {
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lua_pushliteral(L, "caught (...)");
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}
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return lua_error(L); // Rethrow as a Lua error.
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}
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static int myinit(lua_State *L)
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{
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...
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// Define wrapper function and enable it.
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lua_pushlightuserdata(L, (void *)wrap_exceptions);
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luaJIT_setmode(L, -1, LUAJIT_MODE_WRAPCFUNC|LUAJIT_MODE_ON);
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lua_pop(L, 1);
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...
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}
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</pre>
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<p>
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Note that you can only define <b>a single global wrapper function</b>,
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so be careful when using this mechanism from multiple C++ modules.
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Also note that this mechanism is not without overhead.
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</p>
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<br class="flush">
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</div>
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<div id="foot">
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<hr class="hide">
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Copyright © 2005-2013 Mike Pall
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<span class="noprint">
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·
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<a href="contact.html">Contact</a>
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</span>
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</div>
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</body>
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</html>
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